Indications for Testing
Carcinoid syndrome marked by symptoms of flushing and diarrhea, wheezing, right-sided congestive heart failure
Laboratory Testing
- Symptoms should guide laboratory testing for biochemical markers (National Comprehensive Cancer Network [NCCN], 2017)
- Testing for hormones produced by NETs may include
- 5-hydroxyindoleacetic acid (5-HIAA) (urine or plasma) – for flushing
- Metabolic product of serotonin
- Two sequential 24-hour urine samples recommended
- Significant elevation (10 times the upper reference limit) of urine 5-HIAA may indicate the presence of a carcinoid tumor
- Chromogranin A
- Prognostic marker in NETs; elevated levels suggest poorer prognosis (NCCN, 2017)
- Gastrin – fasting concentrations, with individual off proton-pump inhibitors for 1 week
- Prognostic marker in gastric tumors with hypergastrinemia syndrome
- Adrenocorticotropic hormone (ACTH)/cortisol – useful in thymic and bronchial tumors with Cushing syndrome
- Serotonin – whole blood preferred over serum
- Highly specific for carcinoid identification
- Not frequently used
- Neurokinin A – prognostic marker for midgut NETs
- 5-hydroxyindoleacetic acid (5-HIAA) (urine or plasma) – for flushing
Histology
- Definitive diagnosis requires biopsy and pathologist examination
- Useful immunohistochemical stains may include chromogranin A, synaptophysin, and cytokeratin 8,18
- For detailed descriptions, refer to ARUP’s Immunohistochemistry Stain Offerings
Imaging Studies
- Computed tomography (CT)/magnetic resonance imaging (MRI)
- Abdomen and pelvis
- Echocardiography
- For bronchopulmonary effects
- Evaluate valvular thickening and leaflet damage
- Endoscopy
- As indicated by location (esophagogastroduodenoscopy [EGD], colonoscopy)
- Other imaging as indicated
- Bronchoscopy
- CT of chest
- CT enterography or capsule endoscopy
- Endorectal MRI
- Endoscopic ultrasound
- Fluorodeoxyglucose positron emission tomography (FDG-PET)/CT and brain imaging with CT/MRI for poorly differentiated carcinomas
- MRI with gadoxetate
- Somatostatin receptor-based imaging
Differential Diagnosis
- Flushing
- Menopause
- Alcohol abuse
- Pheochromocytoma
- Medullary carcinoma of the thyroid
- Mastocytosis
- Renal cell carcinoma
- VIPoma (vasoactive intestinal polypeptide secreting tumors)
- Wheezing
- Asthma
- Chronic obstructive pulmonary disease
- Anaphylaxis
- Foreign body obstruction
- Pulmonary edema
- Diarrhea
- Infections
- Viral
- Bacterial
- Parasitic
- Autoimmune bowel disease
- Laxative abuse
- Infections
- Heart valve disease
- Rheumatic heart diseases
- Endocarditis
- Cardiomyopathy
- Pulmonary hypertension